Chronobiology may be briefly described as the study of temporal characteristics of biological phenomena. The objective of this biennial conference of the international Society for Chronobiology is to provide a forum for the exchange of current results and theories in the field of biological rhythms. This meeting will provide an opportunity for scientists in the fields of botany, zoology, agricultural sciences, veterinary and human medicine, psychology, psychiatry, mathematics, public health and statistics to exchange ideas. In keeping with the broad nature of the discipline of chronobiology, a wide range of topics will be included on the program. The main theme of the meeting will be the actual and potential application of chronobiological techniques and concepts to maintaining a healthy organism, be it man, lower animal or plant. Emphasis will be placed on optimizing utilization of nutritional substances by living things (optimal energy utilization), on the most efficacious methods of treating patients with drugs and of determining the actual responses of test animals to such drugs in test protocols, and on interfering with rhythms of those organisms that are harmful to man and the environment while maintaining normal or nearly normal rhythms in beneficial species or hosts. While rhythms with a period of about 24 hr (circadian rhythms) will be discussed at length, rhythms with periodicities shorter (ultradian) or longer (infradian) than 24 hr will also be given ample consideration. Circannual rhythms will be emphasized.